Preparation and Evaluation of Ammonium-Succinic Salts as Shale Swelling Inhibitor and Its Application in Water-Based Drilling Fluids

A series of ammonium-succinic salts (ASS) was prepared from succinic acid and amines as small molecule shale swelling inhibitor. It was evaluated by bentonite linear expansion test, anti-swelling experiments. And then the best one, ASS-8 (synthesize with succinic acid and tetraethylenepentamine with the ratio of acid group to amine group 1 : 2), was evaluated in water-based drilling fluid. Anti-swelling results shows that ASS-8 can decrease the swelling volume of bentonite by 90.9% with the concentration of 0.8%. Drilling fluid evaluation sho wed ASS-8 has high inhibitive capability to bentonite hydration swelling in the water-based drilling fluid, and it is compatible with heteropolysaccharide(KD-03) and modified starch. The inhibition mechanism of ASS-8 was studied by thermogravimetric analysis and particle distribution test. These results demonstrate ASS-8 may enter the clay layer and bond the clay sheets together by electrostatic adsorption and hydrogen bonds.